Mechanisms of lifetime degradation in Si/ARC samples patterned by laser lift-off

K. L. Saenger

doi:10.1117/12.930047

12 October 2012 Mechanisms of lifetime degradation in Si/ARC samples patterned by laser lift-off

K. L. Saenger

Proceedings Volume 8473, Laser Material Processing for Solar Energy; 84730S (2012) https://doi.org/10.1117/12.930047
Event: SPIE Solar Energy + Technology, 2012, San Diego, California, United States

Abstract

Applications for laser patterning in Si photovoltaics include (i) patterning SiO₂ or SiN layers with openings for local contacts and (ii) laser-doped selective emitter (LDSE) processes, in which the contact open is accompanied by the diffusion of dopants into a locally melted Si area. While contact open processes are best performed with UV wavelengths that can be strongly absorbed by the SiN or SiO₂ (allowing layer ablation with a minimum of Si heating), the Si melt depth required by LDSE requires irradiation at longer laser wavelengths where these antireflection coatings (ARCs) no longer absorb well. An optimized LDSE process must thus produce Si melting as well as the least amount of Si vaporization sufficient to lift off the overlying ARC. In this work, we investigate the mechanisms for lifetime degradation in Si(p-type, 100-oriented)/ARC samples resulting from 20 ns pulsed laser irradiation at 532 nm at fluences near the threshold for ARC removal. To differentiate between lifetime degradation induced by changes in the passivation layer vs. changes in the Si itself, samples were lifetime mapped after patterned laser irradiation and then again after a wet ARC strip and repassivation. Samples with ARCs of thermal SiO₂ and PECVD SiN typically showed some residual Si damage after irradiation at fluences sufficient for contact open. Interestingly, irradiation of the SiO₂ samples at lower fluences, between the threshold for Si melting and ARC removal, showed damage to the SiO₂ passivation, but no residual Si damage. Explanations for these observations and related results will be discussed.

Citation Download Citation

K. L. Saenger "Mechanisms of lifetime degradation in Si/ARC samples patterned by laser lift-off", Proc. SPIE 8473, Laser Material Processing for Solar Energy, 84730S (12 October 2012); https://doi.org/10.1117/12.930047

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